linux-kernel - Re: [PATCH] parisc: fix module loading failure of large kernel modules (take 4)

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Date:	Thu, 1 Jan 2009 11:22:00 +1030
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	Helge Deller <deller@....de>
Cc:	"linux-parisc" <linux-parisc@...r.kernel.org>,
	Linux Kernel Development <linux-kernel@...r.kernel.org>,
	Kyle McMartin <kyle@...artin.ca>,
	Randolph Chung <randolph@...sq.org>,
	Linus <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Sam Ravnborg <sam@...nborg.org>,
	John David Anglin <dave@...uly1.hia.nrc.ca>
Subject: Re: [PATCH] parisc: fix module loading failure of large kernel modules (take 4)

On Thursday 01 January 2009 00:43:56 Helge Deller wrote:
> Rusty Russell wrote:
> > Not quite what I had in mind... let me show you:
> > ...
> > Otherwise I'd have called it "arch_module_extra_size()".
> 
> This would mean that I can increase the section size in the arch-specific function
> by returning a bigger value than sh_size.
> This would give me space at the end of the section, but not at the beginning 
> (which is what I need), as sh_entsize (the offset into memory) will stay the 
> same as before.

Ah, OK.  I assumed that extra room at the end was sufficient.

So I've taken your previous patch and renamed the function to
arch_mod_section_prepend().  If we decide not to kill those bad gcc versions,
I'll stick it in some other random file (lib/weak.c?  Blech...)

BTW, this is very late for this merge window.  I would have liked to see
this a month ago :(

Subject: module: fix module loading failure of large kernel modules for parisc
Date: Wed, 31 Dec 2008 12:31:18 +0100
From: Helge Deller <deller@....de>

When creating the final layout of a kernel module in memory, allow the
module loader to reserve some additional memory in front of a given section.
This is currently only needed for the parisc port which needs to put the
stub entries there to fulfill the 17/22bit PCREL relocations with large
kernel modules like xfs.

Signed-off-by: Helge Deller <deller@....de>
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au> (renamed fn)

diff --git a/include/linux/moduleloader.h b/include/linux/moduleloader.h
--- a/include/linux/moduleloader.h
+++ b/include/linux/moduleloader.h
@@ -12,6 +12,9 @@ int module_frob_arch_sections(Elf_Ehdr *
 			      Elf_Shdr *sechdrs,
 			      char *secstrings,
 			      struct module *mod);
+
+/* Additional bytes needed by arch in front of individual sections */
+unsigned int arch_mod_section_prepend(struct module *mod, unsigned int section);
 
 /* Allocator used for allocating struct module, core sections and init
    sections.  Returns NULL on failure. */
diff --git a/kernel/module.c b/kernel/module.c
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1588,11 +1588,21 @@ static int simplify_symbols(Elf_Shdr *se
 	return ret;
 }
 
+/* Additional bytes needed by arch in front of individual sections */
+unsigned int __weak arch_mod_section_prepend(struct module *mod,
+					     unsigned int section)
+{
+	/* default implementation just returns zero */
+	return 0;
+}
+
 /* Update size with this section: return offset. */
-static long get_offset(unsigned int *size, Elf_Shdr *sechdr)
+static long get_offset(struct module *mod, unsigned int *size,
+		       Elf_Shdr *sechdr, unsigned int section)
 {
 	long ret;
 
+	*size += arch_mod_section_prepend(mod, section);
 	ret = ALIGN(*size, sechdr->sh_addralign ?: 1);
 	*size = ret + sechdr->sh_size;
 	return ret;
@@ -1632,7 +1642,7 @@ static void layout_sections(struct modul
 			    || strncmp(secstrings + s->sh_name,
 				       ".init", 5) == 0)
 				continue;
-			s->sh_entsize = get_offset(&mod->core_size, s);
+			s->sh_entsize = get_offset(mod, &mod->core_size, s, i);
 			DEBUGP("\t%s\n", secstrings + s->sh_name);
 		}
 		if (m == 0)
@@ -1650,7 +1660,7 @@ static void layout_sections(struct modul
 			    || strncmp(secstrings + s->sh_name,
 				       ".init", 5) != 0)
 				continue;
-			s->sh_entsize = (get_offset(&mod->init_size, s)
+			s->sh_entsize = (get_offset(mod, &mod->init_size, s, i)
 					 | INIT_OFFSET_MASK);
 			DEBUGP("\t%s\n", secstrings + s->sh_name);
 		}
--
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